Thomas Hussenet

Cutaneous cancer stem cell maintenance is dependent on beta-catenin signalling

Continuous turnover of epithelia is ensured by the extensive self-renewal capacity of tissue-specific stem cells. Similarly, epithelial tumour maintenance relies on cancer stem cells (CSCs), which co-opt stem cell properties. For most tumours, the cellular origin of these CSCs and regulatory pathways essential for sustaining stemness have not been identified. In murine skin, follicular morphogenesis is driven by bulge stem cells that specifically express CD34. Here we identify a population of cells in early epidermal tumours characterized by phenotypic and functional similarities to normal bulge skin stem cells. This population contains CSCs, which are the only cells with tumour initiation properties. Transplants derived from these CSCs preserve the hierarchical organization of the primary tumour. We describe β-catenin signalling as being essential in sustaining the CSC phenotype. Ablation of the β-catenin gene results in the loss of CSCs and complete tumour regression. In addition, we provide evidence for the involvement of increased β-catenin signalling in malignant human squamous cell carcinomas. Because Wnt/β-catenin signalling is not essential for normal epidermal homeostasis, such a mechanistic difference may thus be targeted to eliminate CSCs and consequently eradicate squamous cell carcinomas.

SOX2 is an oncogene activated by recurrent 3q26.3 amplifications in human lung squamous cell carcinomas.

Squamous cell carcinoma (SCC) of the lung is a frequent and aggressive cancer type. Gene amplifications, a known activating mechanism of oncogenes, target the 3q26-qter region as one of the most frequently gained/amplified genomic sites in SCC of various types. Here, we used array comparative genomic hybridization to delineate the consensus region of 3q26.3 amplifications in lung SCC. Recurrent amplifications occur in 20% of lung SCC (136 tumors in total) and map to a core region of 2 Mb (Megabases) that encompasses SOX2, a transcription factor gene. Intense SOX2 immunostaining is frequent in nuclei of lung SCC, indicating potential active transcriptional regulation by SOX2. Analyses of the transcriptome of lung SCC, SOX2-overexpressing lung epithelial cells and embryonic stem cells (ESCs) reveal that SOX2 contributes to activate ESC-like phenotypes and provide clues pertaining to the deregulated genes involved in the malignant phenotype. In cell culture experiments, overexpression of SOX2 stimulates cellular migration and anchorage-independent growth while SOX2 knockdown impairs cell growth. Finally, SOX2 over-expression in non-tumorigenic human lung bronchial epithelial cells is tumorigenic in immunocompromised mice. These results indicate that the SOX2 transcription factor, a major regulator of stem cell function, is also an oncogene and a driver gene for the recurrent 3q26.33 amplifications in lung SCC.

SOX2 in squamous cell carcinoma: amplifying a pleiotropic oncogene along carcinogenesis.

SOX2 is a master pluripotency controller that was recently identified as a novel major oncogene, recurrently amplified and activated in Squamous Cell Carcinoma (SCC). These studies have used a similar strategy of chromosomal aberrations screening to identify the SOX2 locus as one of the most frequently amplified site over the SCC genome. They have further highlighted the recurrent SOX2 activation and its necessary role for squamous cell survival. Finally, they showed that SOX2 is also involved in the early steps of lung SCC, as participating to transform human bronchial epithelial cells. Furthermore, SOX2 overexpression can induce the expression of the squamous markers p63 and keratin 6, supporting the idea that SOX2 might be implicated in SCC differentiation. In addition, SOX2 overexpression stimulates lung squamous cell migration. However, neither study assessed the impact of the recurrent activation of SOX2 in advanced primary tumors nor how SOX2 may mechanistically participate to tumor progression and aggressiveness. Here we present these studies and additional data from integrative transcriptomic analyses of primary lung SCC that altogether shed new light and open new exciting perspectives on the multiples roles that SOX2 exerts all along SCC carcinogenesis.

Cyclin L1 (CCNL1) gene alterations in human head and neck squamous cell carcinoma

We evaluated the expression and amplification of cyclin L1 (CCNL1) gene, a potential oncogene localised in the commonly amplified 3q25–28 region, in human head and neck squamous cell carcinomas (HNSCCs). Overexpression was observed in 55 out of 96 cases (57%) and amplification in nine out of 35 tumours (26%) with no relationships to the clinico-pathological parameters. The Cyclin L1 antibody we developed labels nuclear speckles in tumour cells compatible with a role for CCNL1 in RNA splicing.

An adult tissue-specific stem cell molecular phenotype is activated in epithelial cancer stem cells and correlated to patient outcome

Recent studies have shown that embryonic stem cell-like molecular phenotypes are commonly activated in human epithelial primary tumors and are linked to adverse patient prognosis. However it remains unclear whether these correlations to outcome are linked to the differentiation status of the human primary tumours1 or represent molecular reminiscences of epithelial cancer stem cells. In addition, while it has been demonstrated that leukemic cancer stem cells re-acquire an embryonic stem cell-like phenotype, the molecular basis of stem cell function in epithelial cancer stem cells has not been investigated. Here we show that a normal adult tissue-specific stem cell molecular phenotype is commonly activated in epithelial cancer stem cells and for the first time provide evidence that enrichment in cancer stem cells-specific molecular signatures are correlated to highly aggressive tumor phenotypes in human epithelial cancers.

The laminin response in inflammatory bowel disease: protection or malignancy?

Laminins (LM), basement membrane molecules and mediators of epithelial-stromal communication, are crucial in tissue homeostasis. Inflammatory Bowel Diseases (IBD) are multifactorial pathologies where the microenvironment and in particular LM play an important yet poorly understood role in tissue maintenance, and in cancer progression which represents an inherent risk of IBD. Here we showed first that in human IBD colonic samples and in murine colitis the LMα1 and LMα5 chains are specifically and ectopically overexpressed with a concomitant nuclear p53 accumulation. Linked to this observation, we provided a mechanism showing that p53 induces LMα1 expression at the promoter level by ChIP analysis and this was confirmed by knockdown in cell transfection experiments. To mimic the human disease, we induced colitis and colitis-associated cancer by chemical treatment (DSS) combined or not with a carcinogen (AOM) in transgenic mice overexpressing LMα1 or LMα5 specifically in the intestine. We demonstrated that high LMα1 or LMα5 expression decreased susceptibility towards experimentally DSS-induced colon inflammation as assessed by histological scoring and decrease of pro-inflammatory cytokines. Yet in a pro-oncogenic context, we showed that LM would favor tumorigenesis as revealed by enhanced tumor lesion formation in both LM transgenic mice. Altogether, our results showed that nuclear p53 and associated overexpression of LMα1 and LMα5 protect tissue from inflammation. But in a mutation setting, the same LM molecules favor progression of IBD into colitis-associated cancer. Our transgenic mice represent attractive new models to acquire knowledge about the paradoxical effect of LM that mediate either tissue reparation or cancer according to the microenvironment. In the early phases of IBD, reinforcing basement membrane stability/organization could be a promising therapeutic approach.

Inhibition of PlexA1-mediated brain tumor growth and tumor-associated angiogenesis using a transmembrane domain targeting peptide

The neuropilin-plexin receptor complex regulates tumor cell migration and proliferation and thus is an interesting therapeutic target. High expression of neuropilin-1 is indeed associated with a bad prognosis in glioma patients. Q-RTPCR and tissue-array analyses showed here that Plexin-A1 is highly expressed in glioblastoma and that the highest level of expression correlates with the worse survival of patients. We next identified a developmental and tumor-associated pro-angiogenic role of Plexin-A1. Hence, by using molecular simulations and a two-hybrid like assay in parallel with biochemical and cellular assays we developed a specific Plexin-A1 peptidic antagonist disrupting transmembrane domain-mediated oligomerization of the receptor and subsequent signaling and functional activity. We found that this peptide exhibits anti-tumor activity in vivo on different human glioblastoma models including glioma cancer stem cells. Thus, screening Plexin-A1 expression and targeting Plexin-A1 in glioblastoma patients exhibit diagnostic and therapeutic value.

Mapping EGFR1 mutations in patients with lung adenocarcinoma.

IntroductionUnselected lung cancer patients seem unable to gain in terms of survival from treatment with epidermal growth factor receptor (EGFR) inhibitors. Screening for specific molecular targets involves detection of EGFR1 mutations. The aim of our study was to develop a simple set of tests to detect mutations at the tyrosine kinase domain of the EGFR1 gene while avoiding expensive DNA sequencing to select patients eligible for treatment. MethodsDNA samples from 85 adenocarcinoma patients were analyzed. The cohort consisted of 65 female (40 nonsmokers and 25 smokers) and 20 male patients [15 smokers and 5 diagnosed with bronchioloalveolar carcinomas (BAC)]. Different restriction enzymes were identified that recognize mutations at the EGFR1s tyrosine kinase domain. Biocomputing and polymerase chain reaction were used to develop molecular screening tools. ResultsEight mutations were found in 7 patients, of which 5 were female nonsmokers (14.3%), 1 was a male nonsmoker, and 1 a male smoker. Among the mutations that were discovered, 5 (71%) were found at exon 19 and 3 (29%) at exon 20. At exon 19, 4 were deletions found in nonsmoker women, whereas the fifth was a deletion-insertion found in a nonsmoker male patient with BAC. At exon 20, 3 mutations were identified in 2 patients: a duplication (in a nonsmoker woman) and 2 substitutions (in a smoker male with BAC). No mutations were found at exons 18 and 21. Gene copy number was increased in 6 patients (4 female and 2 male) with the highest being found in a smoking female patient diagnosed with BAC. ConclusionMapping of EGFR1 mutations by alternative methods should be used in the screening of patients with non-small cell lung cancer who are candidates for EGFR inhibitor treatment. Patients with an increased EGFR1 copy number could benefit from the monoclonal antibody therapy.